A resistance-changing memory, such as resistive random access memory (ReRAM), uses a voltage, current, heat or else to reversibly change the resistance value of a material to thereby store as information a state different in resistance value of the material, and attracts attention as one of candidates for the replacement device of flash memories. The resistance change memory is suitable for microfabrication and has its ability to configure cross-point cell arrays; furthermore, this type of memory is easy to achieve a multilayered structure of cell array.
As is known, there are two kinds of operation modes for a variable resistive element of ReRAM. One operation mode is to set a high resistive state and a low resistive state by switching the polarity of an applied voltage. This is called the bipolar type. The other operation mode is to enable setup of the high resistive state and low resistive state by controlling both a voltage value and a voltage application time period without having to switch the polarity of an applied voltage. This is known as the unipolar type (see Non-patent Document 1, for example).
To increase the density of storage data of ReRAM, it is effective to set multiple value levels of cell resistance, along with downscaling of the cell size per se. However, in view of the fact that the state of a resistive body is determined by a voltage and heat to be applied to the resistive body, the resistance value of a cell becomes readily influenceable by disturbance occurring in access events. Thus, a need is felt to provide a technique for eliminating this influenceability. In particular, the disturbance occurrable during reading by detection of a resistive state of a cell is inherently unavoidable to resistance change memories of the nondestructive read type, although such disturbance is less in magnitude. Failure to devise this countermeasure would result in degradation of the reliability of ReRAM.
[Non-patent Document 1] Y. Hosoi et al., “High Speed Unipolar Switching Resistance RAM (RRAM) Technology,” IEEE International Electron Devices Meeting 2006 Technical Digest, pp. 793-796.